Two-door elevator

ABSTRACT

An elevator assembly for moving a tubular member, the elevator assembly comprising first and second doors each connected to a front side of a body such that the first and second doors rotate between open and closed positions, wherein the body and the doors collectively encircle the tubular member when the doors are in the closed position, and wherein a center of mass of the elevator assembly remains substantially unchanged regardless of whether the first and second doors are in the open or closed position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/793,782, entitled “TWO-DOOR ELEVATOR,” filed Apr. 21, 2006, thedisclosure of which is hereby incorporated herein by reference.

This application is also related to commonly-assigned PCT ApplicationNo. 2007-______, entitled “TWO-DOOR ELEVATOR,” filed concurrentlyherewith, the disclosure of which is hereby incorporated herein byreference.

This application is also related to commonly-assigned GCC ApplicationNo. ______, entitled “TWO-DOOR ELEVATOR,” filed concurrently herewith,the disclosure of which is hereby incorporated herein by reference.

BACKGROUND

Elevators are hinged mechanisms that close around drillpipe or otherdrill string components to facilitate lowering into or lifting out of awellbore. One type of elevator, sometimes called a “single hinge splitelevator,” has two halves or arms which swing away from the pipe when inan open position. In a closed position, the elevator arms latchtogether, forming a load-bearing ring around the pipe.

Another type of elevator, sometimes called a “side door elevator,” has asingle door that swings open and closed. The “side door” elevator tendsto become imbalanced when the door is open. That is, the weight of thedoor causes the elevator to rotate or tilt toward the door. This canmake the elevator difficult to control. Additionally, engaging the pipewith the elevator is difficult without direct worker intervention.Typically, a worker manually straightens the elevator for engagement andlocking.

The “single hinge split” type elevator also tends to tilt. Additionally,the natural state of this type of elevator is closed, which makes itdifficult to engage the pipe as workers or hydraulics fight against thepull of gravity on the arms. Moreover, heavy ears on the elevator oftenexacerbate the difficulties associated with the “single hinge split”type elevator.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures may not be drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a perspective view of apparatus depicted in a first mode ofoperation according to one or more aspects of the present disclosure.

FIG. 2 is partial perspective view of the apparatus shown in FIG. 1depicted in the operational mode shown in FIG. 1.

FIG. 3 is a perspective view of the apparatus shown in FIG. 1 anddepicted in another mode of operation.

FIG. 4 is a partial perspective view of the apparatus shown FIGS. 1-3depicted in the operational mode shown in FIG. 3.

FIG. 5 is a perspective view of the apparatus shown in FIGS. 1-4depicted in yet another mode of operation.

FIG. 6 is a perspective view of the apparatus shown in FIGS. 1-5depicted in the operational mode shown in FIG. 5.

FIG. 7 is a perspective view of the apparatus shown in FIGS. 1-6depicted in the operational mode shown in FIG. 5.

FIG. 8 is a perspective view of the apparatus shown in FIGS. 1-7depicted in the operational mode shown in FIGS. 1 and 2.

FIG. 9 is a flow-chart diagram of a method according to one or moreaspects of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Moreover, the formation of a first feature over or on a second featurein the description that follows may include embodiments in which thefirst and second features are formed in direct contact, and may alsoinclude embodiments in which additional features may be formedinterposing the first and second features, such that the first andsecond features may not be in direct contact.

The present disclosure relates generally to an elevator for lifting andlowering tubulars or other downhole components, such as pipe or drillstring components. More specifically, the present disclosure is directedtowards an elevator assembly comprising two doors. The doors may beconstructed and connected to the elevator assembly such that the centerof mass of the elevator assembly remains in substantially the samelocation, regardless of whether the doors are open or closed. Theelevator assembly may further comprise one or more spring-lockingassemblies and/or one or more load-locking assemblies. Additionally,cylinders used to open and close the doors may hold the doors inposition.

Referring to FIGS. 1-3 collectively, illustrated are perspective andpartial views of an elevator assembly 100 according to one or moreaspects of the present disclosure. The elevator assembly 100 includes abody 110, a first door 120 a rotatably coupled to the body 110 by afirst hinge pin 125 a, and a second door 120 b rotatably coupled to thebody 110 by a second hinge pin 125 b. The first door 120 a includes aclevis, flange or other attachment means (hereafter referred to as aclevis) 130 a protruding therefrom, and the second door 120 b includes asimilar clevis 130 b protruding therefrom. One end of a compressioncylinder or other type of actuator (such actuator types hereaftercollectively referred to as an actuator) 135 a is pinned or otherwiserotatably coupled to the clevis 130 a of the first door 120 a, whereasthe other end of the actuator 135 a is pinned or otherwise rotatablycoupled to a first flange 140 a extending from the body 110. One end ofanother actuator 135 b is pinned or otherwise rotatably coupled to theclevis 130 b of the second door 120 b, whereas the other end of theactuator 135 b is pinned or otherwise rotatably coupled to a secondflange 140 b extending from the body 110. The elevator assembly 100 alsoincludes ears 145 a, 145 b extending in opposing directions from thebody 110, as well as one or more inserts 150 directly or indirectlycoupled to and/or recessed within the inner diameter 112 of the body110, the first door 120 a and/or the second door 120 b.

The load-locking assembly may include a load-locking cavity or recess124 a in the first door 120 a, and a corresponding load-lockingprojection 124 b in the second door 120 b. Additionally, the second door120 b may have a bottom portion 122 b and a top portion 121 b. The topportion 121 b may include a spring or other device that would tend toseparate the top portion 121 b and the bottom portion 122 b, andpossibly cause some of the top portion 121 b to project above the restof the elevator assembly 100. Upon loading the elevator assembly 100 byengaging a tubular member (not shown), the weight of the collar or otherportion of the tubular member would first engage the top portion 121 bof the second door 120 b. The weight would then overcome the resistanceof the spring in the top portion 121 b, and the top portion 121 b wouldmove downwardly, such that the load-locking projection 124 b in thesecond door 120 b engages the load-locking recess 124 a in the firstdoor 120 a.

For example, in the exemplary embodiment shown in FIGS. 1-3, the seconddoor 120 b includes an upper portion 121 b and a lower portion 122 bwhich are kept in rotational alignment relative to the hinge pin 125 bby alignment guides 123 b, which are best shown in FIG. 3. The upperportion 121 b is free to translate a short distance axially relative tothe lower portion 122 b (in an up-and-down direction relative to thepage in the orientations shown in FIGS. 1-3). However, the upper portion121 b is spring-biased upwards, away from the lower portion 122 b.Consequently, when the elevator 100 is not engaged with a tubularmember, there is a slight gap between the upper portion 121 b and thelower portion 122 b, as best shown in FIG. 3. However, during theoperational mode shown in FIGS. 1 and 2, the weight of a tubular member(not shown) engaged by the elevator 100 urges the upper portion 121 bdown towards the lower portion 122 b. Consequently, a projection 124 bextending from the second door 120 b translates into an aperture 124 aof the first door, thereby locking the first and second doors 120 a, 120b together and preventing them from inadvertently opening.

At least a portion of each of the ears 145 a, 145 b may be integral tothe body. However, as best shown in FIG. 3, a portion of each of theears 145 a, 145 b may include one or more discrete members 147 a, 147 bcoupled to the integral portion of the ears 145 a, 145 b, such as bymechanical fasteners 148 a, 148 b, among other possible coupling means.The ears 145 a, 145 b, including any discrete components 147 a, 147 b,148 a, 148 b thereof, may be mirror-images of each other, or otherwisebe symmetrical relative to the centerline of the elevator 100. The ears145 a, 145 b may additionally be located in a plane substantiallycoinciding with the center of mass of the elevator.

The spring-locking assemblies 155 a, 155 b may have a moveable lockingpin 156 which is held in a position that is outside of a spring-lockingcavity 158 when the door is open. When the door is closed, a lockingspring 157 pushes the moveable locking pin 156 into the spring-lockingcavity 158, causing the door to be locked in the closed position. Inorder to open the door, hydraulic or pneumatic pressure may be used tocompress the locking spring 157.

For example, in the exemplary embodiment shown in FIGS. 1-3, the firstand second doors 120 a, 120 b are locked in a closed position via thespring-locking assemblies 155 a, 155 b, respectively. The lockingassemblies 155 a, 155 b each include a retractable member 156 and aspring 157 which biases the retractable member 156 towards the positionshown in FIG. 2 in which the member 156 is received within an aperture158 of the corresponding first or second door 120 a, 120 b. The spring157 may be or comprise one or more compression springs, Bellvillesprings, and/or other biasing means. As shown in FIG. 4, the member 156is configured to be retracted out of the aperture 158 to unlock thecorresponding first or second door 120 a, 120 b and allow rotation ofthe door around the corresponding hinge pin 125 a, 125 b.

Such retraction may be via pneumatic or hydraulic pressure or vacuumsupplied to an inner chamber 159 of the assemblies 155 a, 155 b. Forexample, each assembly 155 a, 155 b may include a pneumatic or hydraulicfitting 160 for fluidly coupling the inner chamber 159 with a hose orother connection means extending to a pneumatic or hydraulic pressure orvacuum source. In the exemplary embodiment shown in FIGS. 2 and 4, theinner chamber 159 is configured to receive pneumatic or hydraulic fluid,which acts to urge the member 156 against the spring 157, therebyretracting the member 156 from the aperture 158 of the door 120 a.However, other means for retracting the member 156 from the aperture 158are also within the scope of the present disclosure.

Referring to FIG. 5, with continued reference to FIGS. 1-4, illustratedis a perspective view of another mode of operation of the elevator 100in which the actuators 135 a, 135 b have contracted in length and,thereby, opened the first and second doors 120 a, 120 b. The actuators135 a, 135 b may each be or comprise a pneumatic or hydraulic cylinderhaving a cylinder barrel end coupled to the corresponding flange 140 a,140 b, and another end from which extends a piston rod coupled to thecorresponding clevis 130 a, 130 b. The actuators 135 a, 135 b may becoupled to the corresponding flange 140 a, 140 b and clevis 130 a, 130 bby pins, threaded fasteners, and/or other mechanical fastening means 165configured to allow rotation. For example, like the devises 130 a, 130b, the flanges 140 a, 140 b may include a clevis or other flared portionconfigured to receive a flange extending from the cylinder barrel end ofthe actuators 135 a, 135 b and a clevis pin extending therethrough.

The doors 120 a, 120 b, actuators 135 a, 135 b, and/or lockingassemblies 155 a, 155 b may be constructed and positioned within theelevator assembly 100 such that the center of mass of the elevatorassembly 100 remains in substantially the same location regardless ofwhether the doors 120 a, 120 b are in the open position shown in FIG. 5or the closed position shown in FIGS. 1-4. For example, as the doors 120a, 120 b move towards the open position shown in FIG. 5, they would tendto transition the center of mass of the elevator 100 away from thecenter of mass of the elevator 100 when the doors are closed, where suchtransition is generally in a direction similar to the direction in whichthe doors open. However, at the same time the doors 120 a, 120 b areopening, the locking pin 156 of the locking assemblies 155 a, 155 band/or the piston rod of the actuators 135 a, 135 b are moving in adirection opposite to the direction in which the doors are opening. Itis this transition of the mass of the locking pins 156 and/or pistonrods, for example, that counterbalances the movement of the massresulting from opening the doors. Consequently, the elevator 100 canremain neutrally balanced whether the doors are in or moving towards theopen or closed position, or the center of mass of the elevator 100 canotherwise remain substantially unchanged as the doors move between theopen and closed positions. This may, accordingly, reduce or eliminatethe need for a worker to straighten or tilt the elevator assembly 100after it has engaged a tubular member.

Referring to FIGS. 6-8, collectively, illustrated are perspective viewsof the elevator 100 shown in FIGS. 1-5 in the operational mode depictedin FIG. 5 where the elevator 100 is also being engaged with a tubularmember 200. The tubular member 200 is a conventional or future-developedtubular member used in, for example, the oil services industry. Forexample, the tubular member 200 includes a collar 210 having a greaterouter diameter relative to the substantial length of the tubular member200.

In the operational mode shown in FIG. 6, the first and second doors 120a, 120 b are opened by operating the actuators 135 a, 135 b,respectively. The elevator assembly 100 is then oriented relative to thetubular member 200 such that the flanges 140 a, 140 b extending from thebody 110 contact the outer surface of the tubular member 200. Theflanges 140 a, 140 b may be tapered at, for example, about 45° (e.g.,see FIG. 3). Accordingly, the flanges 140 a, 140 b may function to tiltthe elevator assembly 100 into axial alignment with the tubular member200 as a result of the contact between the flanges 140 a, 140 b and theouter surface of the tubular member 200, as shown in FIG. 7. Thereafter,as shown in FIG. 8, the doors 120 a, 120 may be closed around thetubular member 200 by operating the actuators 135 a, 135 b,respectively. As the doors 120 a, 120 b reach the fully closed position,the spring-locking assemblies 155 a, 155 b force the locking pins 156into the locking apertures 158 (e.g., see FIGS. 2 and 4). Subsequently,the elevator assembly 100 may be lifted vertically relative to thetubular member 200, and ultimately the weight of the tubular member 200will bias the upper portion 121 b of the second door 120 b downward toengage the locking pin 124 of the second door 120 b with the lockingaperture 124 a of the first door 120 a (i.e., engaging the load-lockingassembly). Thus, the doors 120 a, 120 b become double-locked, furtherensuring that the tubular member 200 does not inadvertently escape theelevator assembly 100.

Additionally, during the operation described above with respect to FIGS.1-8, the doors 120 a, 120 b may be configured to aid in centralizing theelevator assembly 100 relative to the tubular member 200 when initiallyorienting the elevator assembly 100 relative to the tubular member 200.Moreover, it should be noted that the doors 120 a, 120 b may open andclose concurrently or independently in any sequence, whether suchoperation is manual or automatic, and whether such operation iscontrolled remotely or locally.

As described above, the elevator assembly 100 may also include dyes orinserts 150. The inserts 150 coupled to or otherwise associated with thesecond door 120 b may be fixed to the top portion 121 b and allowed tofloat with respect to the bottom portion 122 b. The remaining inserts150 may all float relative to the body 110 and/or the first door 120 a.In this manner, when a load is introduced, the insert 150 associatedwith the second door 120 b may be configured to move, thereby causingthe top portion 121 b to move downwardly, such that the load-lockingprojection 124 b in the second door 120 b engages the load-lockingrecess 124 a in the first door 120 a. In addition to providing analternative to using a collared tubular, the inserts 150 may also beconfigured to allow the elevator assembly 100 to engage or otherwise beutilized with multiple ranges of tubular sizes, such as in embodimentsin which the inserts 150 are replaceable components effectivelydecreasing or increasing the inner engaging profile of the elevatorassembly 100.

The elevator assembly 100 may also include a failsafe indicator thatprovides the operator with an indication that the doors 120 a, 120 bhave locked. This indicator may be particularly useful for automaticclosing of the doors, whether hydraulic or pneumatic.

Referring to FIG. 9, illustrated is a flow-chart diagram of a method 900for moving a tubular member according to one or more aspects of thepresent disclosure. The method 900 is an exemplary embodiment of theimplementation of one or more of the operational modes described abovewith respect to FIGS. 1-8, and may utilize the elevator assembly 100shown in FIGS. 1-8.

The method 900 includes a step 910 comprising orienting an elevatorassembly around the tubular member such that the axis of the elevatorassembly is substantially aligned with the axis of the tubular member.The method 900 also includes a step 920 comprising closing the elevatorassembly around the tubular, wherein the elevator assembly comprisesfirst and second doors each connected to a front side of a body suchthat the first and second doors rotate between open and closedpositions, wherein the body and the doors collectively encircle thetubular member when the doors are in the closed position, and wherein acenter of mass of the elevator assembly remains substantially unchangedregardless of whether the first and second doors are in the open orclosed position. The method 900 also includes a step 930 comprisinglocking the elevator assembly doors in the closed position.

The closing step 920 may comprise pneumatically or hydraulicallyoperating first and second actuators operable to open and close thefirst and second doors. The locking step 930 may comprise insertingfirst and second locking pins into corresponding first and secondcavities, respectively, in the first and second doors, respectively. Thelocking step 930 may alternatively or additionally comprise applying anaxial load to a top part of the second door thereby translating the toppart of the second door towards a bottom part of the second doorresulting in the insertion of a locking projection extending from thetop part of the second door into a corresponding cavity in the firstdoor.

In view of all of the above and FIGS. 1-8, it should be clear to thoseskilled in the art that the present disclosure introduces an elevatorassembly for moving a tubular member, the elevator assembly comprisingfirst and second doors each connected to a front side of a body suchthat the first and second doors rotate between open and closedpositions, wherein the body and the doors collectively encircle thetubular member when the doors are in the closed position, and wherein acenter of mass of the elevator assembly remains substantially unchangedregardless of whether the first and second doors are in the open orclosed position. The elevator assembly may further comprise first andsecond spring-locking assemblies configured to lock the first and seconddoors, respectively, in the closed position. The first and secondspring-locking assemblies may each include a locking pin biased towardsthe corresponding first or second door and configured to be receivedwithin a locking aperture of the first or second door when the first orsecond door is in the closed position. The elevator assembly may furthercomprise a load-locking assembly configured to lock the doors in theclosed position upon application of an axial load to the elevatorassembly. The load-locking assembly may comprise a load-locking cavitylocated in the first door and a load-locking projection extending fromthe second door, wherein the application of the axial load results fromthe weight of the tubular member and causes the load-locking projectionto enter the load-locking cavity. The elevator assembly may furthercomprise first and second actuators operable to open and close the firstand second doors, respectively. The actuators may be hydraulic actuatorsor pneumatic actuators.

The present disclosure also introduces a method for moving a tubularmember, comprising orienting an elevator assembly around the tubularmember such that the axis of the elevator assembly is substantiallyaligned with the axis of the tubular member, closing the elevatorassembly around the tubular, wherein the elevator assembly comprisesfirst and second doors each connected to a front side of a body suchthat the first and second doors rotate between open and closedpositions, wherein the body and the doors collectively encircle thetubular member when the doors are in the closed position, and wherein acenter of mass of the elevator assembly remains substantially unchangedregardless of whether the first and second doors are in the open orclosed position, and locking the elevator assembly doors in the closedposition. Closing the elevator assembly may comprise pneumatically orhydraulically operating first and second actuators operable to open andclose the first and second doors. Locking the elevator assembly doors inthe closed position may comprise inserting first and second locking pinsinto corresponding first and second cavities, respectively, in the firstand second doors, respectively. Locking the elevator assembly doors inthe closed position may alternatively or additionally comprise applyingan axial load to a top part of the second door thereby translating thetop part of the second door towards a bottom part of the second doorresulting in the insertion of a locking projection extending from thetop part of the second door into a corresponding cavity in the firstdoor.

The present disclosure also introduces an elevator assembly for moving atubular member, comprising first and second doors each connected to afront side of a body such that the first and second doors rotate betweenopen and closed positions, wherein the body and the doors collectivelyencircle the tubular member when the doors are in the closed position,and first and second spring-locking assemblies configured to lock thefirst and second doors, respectively, in the closed position. The firstand second spring-locking assemblies may each include a locking pinbiased towards the corresponding first or second door and configured tobe received within a locking aperture of the first or second door whenthe first or second door is in the closed position. The elevatorassembly may further comprise a load-locking assembly configured to lockthe doors in the closed position upon application of an axial load tothe elevator assembly. The load-locking assembly may comprise aload-locking cavity located in the first door and a load-lockingprojection extending from the second door, wherein the application ofthe axial load results from the weight of the tubular member and causesthe load-locking projection to enter the load-locking cavity. Theelevator assembly may further comprise first and second actuatorsoperable to open and close the first and second doors, respectively. Theactuators may be hydraulic or pneumatic actuators.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. An elevator assembly for moving a tubular member, comprising: firstand second doors each connected to a front side of a body such that thefirst and second doors rotate between open and closed positions, whereinthe body and the doors collectively encircle the tubular member when thedoors are in the closed position, and wherein a center of mass of theelevator assembly remains substantially unchanged regardless of whetherthe first and second doors are in the open or closed position.
 2. Theelevator assembly of claim 1 further comprising first and secondspring-locking assemblies configured to lock the first and second doors,respectively, in the closed position.
 3. The elevator assembly of claim2 wherein the first and second spring-locking assemblies each include alocking pin biased towards the corresponding first or second door andconfigured to be received within a locking aperture of the first orsecond door when the first or second door is in the closed position. 4.The elevator assembly of claim 1 further comprising a load-lockingassembly configured to lock the doors in the closed position uponapplication of an axial load to the elevator assembly.
 5. The elevatorassembly of claim 4 wherein the load-locking assembly comprises aload-locking cavity located in the first door and a load-lockingprojection extending from the second door, and wherein the applicationof the axial load results from the weight of the tubular member andcauses the load-locking projection to enter the load-locking cavity. 6.The elevator assembly of claim 1 further comprising first and secondactuators operable to open and close the first and second doors,respectively.
 7. The elevator assembly of claim 6 wherein the actuatorsare hydraulic actuators.
 8. The elevator assembly of claim 6 wherein theactuators are pneumatic actuators.
 9. A method for moving a tubularmember, comprising: orienting an elevator assembly around the tubularmember such that the axis of the elevator assembly is substantiallyaligned with the axis of the tubular member; closing the elevatorassembly around the tubular, wherein the elevator assembly comprisesfirst and second doors each connected to a front side of a body suchthat the first and second doors rotate between open and closedpositions, wherein the body and the doors collectively encircle thetubular member when the doors are in the closed position, and wherein acenter of mass of the elevator assembly remains substantially unchangedregardless of whether the first and second doors are in the open orclosed position; and locking the elevator assembly doors in the closedposition.
 10. The method of claim 9 wherein closing the elevatorassembly comprises pneumatically operating first and second actuatorsoperable to open and close the first and second doors.
 11. The method ofclaim 9 wherein closing the elevator assembly comprises hydraulicallyoperating first and second actuators operable to open and close thefirst and second doors.
 12. The method of claim 9 wherein locking theelevator assembly doors in the closed position comprises inserting firstand second locking pins into corresponding first and second cavities,respectively, in the first and second doors, respectively.
 13. Themethod of claim 9 wherein locking the elevator assembly doors in theclosed position comprises applying an axial load to a top part of thesecond door thereby translating the top part of the second door towardsa bottom part of the second door resulting in the insertion of a lockingprojection extending from the top part of the second door into acorresponding cavity in the first door.
 14. An elevator assembly formoving a tubular member, comprising: first and second doors eachconnected to a front side of a body such that the first and second doorsrotate between open and closed positions, wherein the body and the doorscollectively encircle the tubular member when the doors are in theclosed position; and first and second spring-locking assembliesconfigured to lock the first and second doors, respectively, in theclosed position.
 15. The elevator assembly of claim 14 wherein the firstand second spring-locking assemblies each include a locking pin biasedtowards the corresponding first or second door and configured to bereceived within a locking aperture of the first or second door when thefirst or second door is in the closed position.
 16. The elevatorassembly of claim 14 further comprising a load-locking assemblyconfigured to lock the doors in the closed position upon application ofan axial load to the elevator assembly.
 17. The elevator assembly ofclaim 16 wherein the load-locking assembly comprises a load-lockingcavity located in the first door and a load-locking projection extendingfrom the second door, and wherein the application of the axial loadresults from the weight of the tubular member and causes theload-locking projection to enter the load-locking cavity.
 18. Theelevator assembly of claim 14 further comprising first and secondactuators operable to open and close the first and second doors,respectively.
 19. The elevator assembly of claim 18 wherein theactuators are hydraulic actuators.
 20. The elevator assembly of claim 18wherein the actuators are pneumatic actuators.